EP0434001B1

Movatterモバイル変換

Info

Publication number: EP0434001B1
Application number: EP90124623A
Authority: EP
Inventors: Akira Kaneko; Toru Kanno; Kaoru Tomii
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1989-12-19
Filing date: 1990-12-18
Publication date: 1996-04-03
Anticipated expiration: 2010-12-18
Also published as: DE69026353T2; US5243252A; EP0434001A2; EP0434001A3; DE69026353D1

Description

Background of theInvention

1. Field of the Invention

The present invention relates to an electron emission device for use as a source for electrons in an electron microscope, an electron beam exposure apparatus, a planar image display, or any of various other applications using an electron beam,and a method of manufacturing such an electron emission device.

2. Prior Art

From WO-A-8 909 479 is known a method for the fabrication of field emission type sources and applications thereof. Disclosed is in this document a method for fabrication of field emission peaks using a monocrystalline substrate with a suitable orientation coated with an insulating layer, where square-shaped elementary zones with a suitable orientation with respect to the substrate have been removed. Silicon is disposed by selective epitaxy in these zones. The epitaxial growth of silicon, at high speed parallel to the substrate and at low speed along faces of the substrate at 45° to the substrate, enables the making of pyramidal peaks which, after being coated with tungsten, form emitting peaks.
Hot cathodes for emitting electrons by thermionic emission are used as the source for electrons in various electron beam devices such as an electron microscope, an electron beam exposure apparatus, or a planar image display. The hot cathode requires a heater for heating the cathode itself, and hence causes a loss of energy because of the heating of the cathode.
Recent years have seen the advent of an electron emitter, known as a cold cathode, which does not depend on heat for electron emission. There have been proposed various electron emission devices incorporating the cold cathode. According to one electron emission device, a PN junction is reverse-biased to bring about an electron avalanche breakdown for electron emission. Another electron emission device is of the MIM type which has a three-layer structure composed of a metal layer, an insulation layer, and a metal layer. When a voltage is applied between the metal layers, electrons are forced to pass through the insulation layer due to the tunnel effect, and emitted out of a metal layer surface. Still another electron emission device, which operates on the principle of field emission, has a specially shaped metal surface to which a voltage is applied to develop a localized highly intensive electric field which emits electrons out of the metal surface.
One field-emission-type electron emission device has a cathode emitter whose end is machined into a sharply pointed needle tip having a curvature of several hundreds nm or smaller so that a concentrated electric field of about 10⁷ V/cm will be developed at the pointed needle tip. The field-emission-type electron emission device of this type offers the following advantages:

(1) It has a high current density.
(2) Any consumption of electric energy is very small as the cathode emitter requires no heating.
(3) The device can be used as point and linear sources for electron beams.

A field-emission-type electron emission device is shown in Journal of Applied Physics, Vol. 39, No. 7, Page 3504, 1956, for example. FIG. 1(a) of the accompanying drawings shows such a known field-emission-type electron emission device in the process of being manufactured. FIG. 1(b) illustrates the field-emission-type electron emission device as it is completed.
The field-emission-type electron emission device is manufactured as follows: As shown in FIG. 1(a), an electricallyconductive film 102, an electricallyinsulative layer 103, and an electricallyconductive film 104 are successively evaporated on an electricallyinsulative substrate 101. Theconductive film 104 and theinsulative layer 103 are selectively etched away to produce an array ofcavities 105 therein according to a photolithographic process. Thereafter, while the open ends of thecavities 105 are being progressively closed by a suitable material 106 according to the rotary slant evaporation process, acathode material 107 is evaporated on theconductive film 102 through the open ends of thecavities 105, thereby forming upwardly pointedcathode emitter projections 108 on theconductive film 102 within thecavities 105. Thereafter, the evaporated material 106 is removed, completing the electron emission device as shown in FIG. 1(b).
A power supply 109 is connected to theconductive films 104, 102 such that theconductive film 104 is kept at a positive potential and theconductive film 102 is kept at a negative potential. When a voltage higher than a predetermined voltage that is determined by thecathode material 107 is applied between theconductive films 104, 102, a concentrated electric field is developed which causes thecathode emitter projections 108 to emit electrons.
An effort has been directed to a planar display which comprises an array of such electron emission devices (see Japan Display, 1986, page 512).
Japanese Patent Publication No. 54(1979)-17551 discloses another conventional electron emission device. FIGS. 2(a) through 2(f) of the accompanying drawings show a process of successive steps for manufacturing such a conventional electron emission device.
First, as shown in FIG. 2(a), athin film 122 of a cathode material is evaporated on one surface of each of a plurality of rectangular, electricallyinsulative substrates 121, thus producing a plurality ofsubstrates 123. Then, thesubstrates 123 are superposed to provide aunitary substrate 124, after which the surfaces of thesubstrate 124 are machine-ground. Then, as shown in FIG. 2(b), ametal film 125 is evaporated on one of the wider surfaces of thesubstrate 124.Electron emission windows 126, which are as narrow as thethin films 122, are defined in themetal film 125 directly over the respectivethin films 122 by a photoetching process, as shown in FIG. 2(c). Then, thesubstrates 123 are separated from each other, and thethin film 122 of eachsubstrate 123 is etched into acathode emitter 127 having a pointed triangular pattern, as shown in FIG. 2(d). Thereafter, as shown in FIG. 2(e), eachsubstrate 121 is partially chemically eroded away to produce acavity 128 such that the pointed ends of thecathode emitter 127 are spaced from thesubstrate 121 and the edge of themetal film 125 along theelectron emission window 126 overhangs. As shown in FIG. 2(f), thesubstrates 123 are superposed again and fixed together, thus producing a thin-film cold-cathode array.
The production of the electron emission device shown in FIGS. 1(a) and 1(b) is disadvantageous in that it is very difficult to control the two simultaneous evaporation processes, i.e., for depositing the material 106 and thecathode emitter projections 108 simultaneously.
With the electron emission device shown in FIGS. 2(a) through 2(f), the thicknesses of theinsulative substrates 121 and thethin films 122 must be highly accurate in order to position theelectron emission windows 126 and the cathode emitters 127 in accurate alignment with each other. Furthermore, difficulty has been experienced in fixing thesubstrates 123 with the same degree of accuracy when they are first assembled into thesubstrate 124 and subsequently put together into the final product.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an electron emission device which is simple in construction, can be manufactured easily with a high yield, and is highly reliable in operation, and a method of manufacturing such an electron emission device.
Another object of the present invention is to provide an electron emission device which is capable of emitting a highly defined high-quality electron beam, and a method of manufacturing such an electron emission device.
Still another object of the present invention is to provide an electron emission device which can emit electrons highly efficiently, and a method of manufacturing such an electron emission device.
According to the present invention, there is provided an electron emission device comprising a cathode layer having an edge, and a control electrode spaced and electrically insulated from the cathode layer, for drawing electrons from the edge of the cathode layer.
The electron emission device further includes an insulative substrate, the cathode layer having at least a portion of a rectangular shape, and being disposed on the insulative substrate, and an insulative layer disposed on the insulative substrate on each or one side of the cathode layer, the control electrode being disposed on the insulative layer. The insulative layer is as thick as or thicker than the cathode layer.
The electron emission device also includes a plurality of parallel cathode layers spaced at a predetermined pitch, and a plurality of parallel control electrodes spaced at a predetermined pitch and extending perpendicularly to the cathode layers. The cathode layers and the control electrodes jointly provide a plurality of electron emission areas where the cathode layers and the control electrodes intersect with each other, each of the electron emission regions being of a zigzag shape.
Alternatively, the electron emission device further includes an insulative substrate, the cathode layer being disposed on the insulative substrate, and an insulative layer disposed on the insulative substrate inwardly of the cathode layer, the control electrode being disposed on the insulative layer.
The electron emission device further includes a conductive layer extending through the insulative layer and electrically connected to the control electrode on the insulative layer. The control electrode has a bottom surface as high as or higher than a surface of the cathode layer remote from the insulative substrate.
Alternatively, the electron emission device further has an insulative substrate, the cathode layer being disposed on the insulative substrate, the control electrode comprising first and second control electrodes, a first insulative,layer disposed on the cathode layer, the first control electrode being disposed on the first insulative layer, and a second insulative layer disposed on the insulative substrate, the second control electrode being disposed on the second insulative layer outwardly of the cathode layer, the first insulative layer, and the first control electrode, the first and second control electrodes being electrically connected to each other.
The electron emission device also includes a third insulative layer disposed on portions of the cathode layer and the insulative substrate, and an electric connector disposed on the third insulative layer, the first and second control electrodes being electrically connected to each other by the electric connector.
Alternatively, the electron emission device further includes a third insulative layer disposed on the insulative substrate, and an electric connector extending through the cathode layer, the first insulative layer, the third insulative layer, and the second insulative layer, the first and second control electrodes being electrically connected to each other by the electric connector.
The electron emission device further includes a fourth insulative layer disposed on the second control electrode, and a third control electrode disposed on the fourth insulative layer.
Alternatively, the electron emission device further includes an insulative substrate, the cathode layer having a wedge-shaped portion having a progressively varying width, and an insulative layer disposed on the insulative substrate outwardly of cathode layer, the control electrode being disposed on the insulative layer.
The electron emission device further includes a base electrode disposed on the insulative substrate, the cathode layer being disposed on the base electrode. The electron emission device also has a second insulative layer disposed on at least a surface of the base electrode which is free from the cathode layer, the first-mentioned insulative layer being disposed on the second insulative layer. The first-mentioned insulative layer is as thick as or thicker than the cathode layer.
The electron emission device includes a plurality of parallel striped base electrodes spaced at a predetermined pitch, and a plurality of parallel control electrodes spaced at a predetermined pitch and extending perpendicularly to the base electrodes, whereby the base and control electrodes jointly provide a matrix construction.
According to the present invention, there is also provided a method of manufacturing an electron emission device, comprising the steps of depositing a cathode layer having an edge on an insulative substrate, depositing a material, different from the material of the cathode layer, on the cathode layer, thereafter successively depositing an insulative layer and a metal film on the insulative substrate and the deposited material, removing the deposited material, together with the insulative layer and the metal film thereon, from the cathode layer, and etching the insulative material and the metal film to form a control electrode, which is composed of the etched metal film, on the insulative material on each or one side of the cathode layer.
According to the present invention, there is also provided a method of manufacturing an electron emission device, comprising the steps of depositing a cathode layer having an edge on an insulative substrate, depositing a metal material, different from the material of the cathode layer, all over the cathode layer by plating, thereafter successively depositing an insulative layer and a metal film on the insulative substrate and the metal material, and removing the metal material, together with the insulative layer and the metal film thereon, from the cathode layer to form a control electrode, which is composed of the metal film, on the insulative material on each or one side of the cathode layer.
According to the present invention, there is further provided a method of manufacturing an electron emission device, comprising the steps of depositing a base electrode on an insulative substrate, successively depositing a cathode layer and a covering layer of a material, which is different from the material of the cathode layer, on the base electrode, etching the covering layer and the cathode layer into a wedge shape having a gradually varying width, processing at least a surface of the base electrode, which is free from the cathode layer, into a first insulative layer by anodization or thermal oxidization, successively depositing a second insulative layer and a control electrode on the first insulative layer and the covering layer, and thereafter, removing the covering layer with the second insulative layer and the control electrode thereon. The method further includes the step of etching the cathode layer into a pattern smaller than the covering layer.
According to the present invention, there is also provided a method of manufacturing an electron emission device, comprising the steps of depositing a base electrode on an insulative substrate, depositing a first insulative layer on the base electrode, the first insulative layer having the same pattern as a cathode layer having a wedge shape having a gradually varying width, processing at least a surface of the base electrode, which is free from the first insulative layer, into a second insulative layer by anodization or thermal oxidization, removing the first insulative layer, successively depositing a cathode layer and a covering layer, which is different from the material of the cathode layer, on the base electrode, etching the covering layer and the cathode layer in one pattern at substantially the same position as the removed first insulative layer, depositing a third insulative layer and a control electrode on the first insulative layer and the covering layer, and thereafter removing the covering layer with the third insulative layer and the control electrode thereon. The third insulative layer is disposed outwardly of the cathode layer and is as thick as or thicker than the cathode layer. The method also includes the step of etching the cathode layer into a pattern smaller than the covering layer, and also the step of insulating the base electrode except an area thereof which is as large as or smaller than the pattern of the cathode layer.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a cross-sectional view of a conventional electron emission device as it is in the process of being manufactured;
FIG. 1(b) is a cross-sectional view of the conventional electron emission device as it is completed;
FIGS. 2(a) through 2(f) are views showing a process of manufacturing another conventional electron emission device;
FIGS. 3(a) and 3(b) are perspective and cross-sectional views, respectively, of an electron emission device according to a first embodiment of the present invention;
FIGS. 4(a) through 4(h) are fragmentary cross-sectional views showing a process of manufacturing the electron emission device according to the first embodiment;
FIGS. 5(a) through 5(e) are fragmentary cross-sectional views showing another process of manufacturing the electron emission device according to the first embodiment;
FIGS. 6(a) through 6(d) are fragmentary cross-sectional views showing still another process of manufacturing the electron emission device according to the first embodiment;
FIG. 7 is a fragmentary perspective view of an electron emission device according to a second embodiment of the present invention, the electron emission device being incorporated in a planar display panel;
FIG. 8 is a fragmentary plan view of an electron emission device according to a third embodiment of the present invention, the electron emission device being incorporated in a matrix electron emission source;
FIGS. 9 and 10 are cross-sectional and perspective views, respectively, of an electron emission device according to a fourth embodiment of the present invention;
FIGS. 11(a) through 11(e) are cross-sectional views showing a process of manufacturing the electron emission device according to the fourth embodiment;
FIG. 12 is a cross-sectional view of an electron emission device according to a fifth embodiment of the present invention;
FIGS. 13(a) through 13(e) are cross-sectional views showing a process of manufacturing the electron emission device according to the fifth embodiment;
FIG. 14 is a cross-sectional view of an electron emission device according to a sixth embodiment of the present invention;
FIG. 15 is a cross-sectional view of an electron emission device according to a seventh embodiment of the present invention;
FIGS. 16(a) through 16(c) are plan views of electron emission devices according to eighth through tenth embodiments, respectively, of the present invention;
FIG. 17(a) is a plan view of an electron emission device according to an eleventh embodiment of the present invention;
FIG. 17(b) is a cross-sectional view taken along line 17(b) - 17(b) of FIG. 17(a);
FIG. 17(c) is a cross-sectional view taken along line 17(c) - 17(c) of FIG. 17(a);
FIG. 18(a) is a plan view of an electron emission device according to a twelfth embodiment of the present invention;
FIG. 18(b) is a cross-sectional view taken along line 18(b) - 18(b) of FIG. 18(a);
FIG. 19 is a cross-sectional view of an electron emission device according to a thirteenth embodiment of the present invention;
FIGS. 20(a) through 20(g) are cross-sectional views showing a process of manufacturing the electron emission device according to the thirteenth embodiment;
FIG. 21(a) is a plan view of an electron emission device according to a fourteenth embodiment of the present invention;
FIG. 21(b) is a cross-sectional view taken along line 21(b) - 21(b) of FIG. 21(a);
FIG. 21(c) is a cross-sectional view taken along line 21(c) - 21(c) of FIG. 21(a);
FIGS. 22(a) through 22(f) are cross-sectional views showing a process of manufacturing the electron emission device according to the fourteenth embodiment;
FIGS. 23(a) through 23(g) are cross-sectional views showing another process of manufacturing the electron emission device according to the fourteenth embodiment;
FIG. 24(a) is a fragmentary plan view of an electron emission device according to a fifteenth embodiment of the present invention, the electron emission device being incorporated in a planar display panel; and
FIG. 24(b) is a cross-sectional view taken along line 24(b) - 24(b) of FIG. 24(a).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Like or corresponding parts are denoted by like or corresponding reference numerals throughout views.
FIGS. 3(a) and 3(b) show an electron emission device in accordance with a first embodiment of the present invention.
As shown in FIGS. 3(a) and 3(b), alayer 2 of a cathode material is disposed on an electricallyinsulative substrate 1 of glass or the like. The cathode material of thelayer 2 comprises a material having a low work function and a high melting point, such as SiC, ZrC, TiC, Mo, W, or the like. Thelayer 2 has a thickness of 1000 Å or more and has a rectangular cross section. Thelayer 2 hasopposite edges 2a, 2b on its upper surface. The width W of thelayer 2 is determined depending on the manner in which the electron emission device is used, and should not be limited to any particular dimension. Two electricallyinsulative layers 3 are disposed on theinsulative substrate 1 one on each side of thelayer 2 in spaced relation thereto. Each of theinsulative layers 3 is made of Al₂O₃, SiO₂, or the like, and has a thickness which is at least the same as the thickness of thelayer 2. Only oneinsulative layer 3 may be disposed on one side of thelayer 2 on theinsulative substrate 1. On the insulative layers 3, there are disposedrespective control electrode 4 for drawing electrons from theedges 2a, 2b of thecathode layer 2. Each of thecontrol electrodes 4 comprises a metal film of Mo, Ta, W, or the like. Since the thickness of theinsulative layers 3 is the same as or greater than the thickness of thelayer 2, the bottom surfaces 4a of thecontrol electrodes 4 are located at a height that is the same as or higher than the height of the upper surface 2c of thelayer 2.
The electron emission device shown in FIGS. 3(a) and 3(b) operates as follows:
Thelayer 2 and thecontrol electrodes 4 are connected to a power supply (not shown) such that thelayer 2 is held at a positive potential and thecontrol electrodes 4 at a negative potential. When a voltage higher than a predetermined voltage depending on the cathode material of thelayer 2 is applied between thelayer 2 and thecontrol electrodes 4, a developed electric field is concentrated onedges 2a, 2b of thelayer 2 to cause theedges 2a, 2b to emit electrons into a surrounding evacuated space. The emitted electrons travel along electric lines of force that are determined under the applied voltage between thecontrol electrodes 4 and thelayer 2. Some of the electrons enter thecontrol electrodes 4, while the other electrons fly upwardly of thecontrol electrodes 4. Inasmuch as the bottom surfaces 4a of thecontrol electrodes 4 are as high as or higher than the upper surface 2c of thelayer 2, the electrons emitted from theedges 2a, 2b travel at a velocity whose upward component is large. Therefore, the number of electrons flying over or upwardly of thecontrol electrodes 4, i.e., the intensity of the electron beams from theedges 2a, 2b, is increased. Since theedges 2a, 2b of thelayer 2 are disposed in confronting relation to thecontrol electrodes 4, respectively, the electric field produced between thecontrol electrodes 4 and thecathode layer 2 is concentrated on theedges 2a, 2b, thus increasing the effective field strength at theedges 2a, 2b for electron emission, with the advantage that the voltage applied to emit electrons may be reduced.
A process of manufacturing the electron emission device shown in FIGS. 3(a) and 3(b) will be described below with reference to FIGS. 4(a) through 4(h).
First, as shown in FIG. 4(a), aphotoresist 5 is deposited on the surface of a transparent, electrically insulativesubstrate 1 of glass or the like, except an area where alayer 2 of cathode material is to be deposited. Then, a cathode material is deposited on thesubstrate 1 and thephotoresist 5 to a thickness of 1000 Å or more by vacuum evaporation, sputtering, or the like, after which thephotoresist 5 is removed. Thus, thelayer 2 of cathode material is now formed on thesubstrate 2 in a pattern shown in FIG. 4(b). The above liftoff method which is used to deposit thelayer 2 on thesubstrate 1 allows thelayer 2 to havesharp edges 2a, 2b on its opposite sides for a higher electron emission efficiency. Alternatively, after a cathode material has been deposited on the surface of thesubstrate 1, the deposited cathode material may be selectively etched away to leave alayer 2 on thesubstrate 1 in the pattern shown in FIG. 4(b). Thereafter, as shown in FIG. 4(c), apositive photoresist 6 is coated on thesubstrate 1 and thelayer 2, and then exposed to aparallel beam 7 of ultraviolet radiation which is applied to the surface of thesubstrate 1 opposite to thelayer 2. The exposedphotoresist 6 is then developed by a developing solution into the same photoresist pattern as thelayer 2, as shown in FIG. 4(d). As shown in FIG. 4(e), an electrically insulative material such as Al₂O₃, SiO₂, or the like, which will form electricallyinsulative layers 3, is deposited on the entire surface formed thus far to a thickness which is the same as or greater than thelayer 2, by vacuum evaporation or the like. Then, a metal film, which will formcontrol electrodes 4 for drawing electrons, is deposited on the insulative material to a thickness ranging from 1000 Å to 5000 Å. When thephotoresist 6 is thereafter removed, the insulative material and the metal film over thelayer 2 are also removed, as shown in FIG. 4(f). As shown in FIG. 4(g), only the insulative material is partly etched away, providing aninsulative layer 3 spaced from thelayer 2, which has exposededges 2a, 2b as shown in FIG. 4(h). Then, the metal film is also partly etched away, providingcontrol electrodes 4 which have confronting edges spaced from each other by a distance slightly larger than the width W of thelayer 2. The insulative material and the metal layer may be simultaneously etched using a mixture of etching solutions respectively for the insulating material and the metal layer. If thephotoresist 6 is developed in the step shown in FIG. 4(d) so that it is left so as to cover thelayer 2 and have a width slightly greater than the width W of thelayer 2, then the steps shown in FIGS. 4(g) and 4(h) may be dispensed with.
FIGS. 5(a) through 5(e) show another process of manufacturing the electron emission device shown in FIGS. 3(a) and 3(b).
The manufacturing steps of the process shown in FIGS. 5(a) through 5(e) correspond to the steps shown in FIGS. 4(b) through 4(d), but differ therefrom with respect to the steps shown in FIGS. 4(c) and 4(d). Those parts in FIGS. 5(a) through 5(e) which are identical to those in FIGS. 4(b) through 4(d) are denoted by identical reference numerals. The step shown in FIG. 5(a) is the same as the step shown in FIG. 4(b), in which alayer 2 of cathode material is deposited in a certain pattern on a transparent, electrically insulativesubstrate 1. Then, as shown in FIG. 5(b), anegative photoresist 8 is coated on thesubstrate 1 and thelayer 2, and then exposed to aparallel beam 7 of ultraviolet radiation which is applied to the surface of thesubstrate 1 opposite to thelayer 2. The exposedphotoresist 6 is then developed by a developing solution, removing the photoresist layer from the surface of thelayer 2, as shown in FIG. 5(c). Then, as shown in FIG. 5(d), ametal layer 9 of Ni, Cu, or the like is deposited on the surface formed thus far by electroless plating, or ametal layer 9 of Al or the like is deposited on the surface formed thus far by evaporation, sputtering, or the like. Thereafter, thephotoresist 8 is removed together with the metal layer thereon, leaving themetal layer 9 only on thelayer 2, as shown in FIG. 5(e). The assembly will then be processed in the same manner as the steps shown in FIGS. 4(e) through 4(h). The process shown in FIGS. 5(a) through 5(e) is suitable when a heat treatment, which involves temperatures higher than thephotoresist 6 would resist, is to be carried out to achieve increased bonding strength between theinsulative substrate 1 and theinsulative layers 3 and also between theinsulative layers 3 and thecontrol electrodes 4 at the time theinsulative layer 3 and thecontrol electrode 4 are formed.
FIGS. 6(a) through 6(d) show still another process of manufacturing the electron emission device shown in FIGS. 3(a) and 3(b).
Those parts shown in FIGS. 6(a) through 6(d) which are identical to those in FIGS. 4(a) through 4(h) are denoted by identical reference numerals. First, as shown in FIG. 6(a), alayer 2 of cathode material is deposited in a certain pattern on a transparent, electrically insulativesubstrate 1. Then, as shown in FIG. 6(b), ametal 10 which is different from the cathode material is plated on thelayer 2 and also an area of thesubstrate 1 surrounding thelayer 2. Thereafter, as shown in FIG. 6(c), an electrically insulative material such as Al₂O₃, SiO₂, or the like, which will forminsulative layers 3, is deposited on the entire surface formed thus far by vacuum evaporation, sputtering, or the like, and then a metal film, which will formcontrol electrodes 4, is deposited on the insulative material. Thereafter, the platedmetal 10 is etched away from theinsulative substrate 1, thereby providing the electron emission device as shown in FIG. 6(d). The metal of thecontrol electrodea 4 differs from the platedmetal 10, so that thecontrol electrodes 4 are not eroded when themetal 10 is etched away.
An electron emission device according to a second embodiment of the present invention, which is incorporated in a planar display panel, will now be described with reference to FIG. 7.
As shown in FIG. 7, the electron emission device has a plurality of parallel elongatestriped layers 2 of cathode material disposed on an electricallyinsulative substrate 1, thelayers 2 extending in the vertical direction indicated by the arrow V and spaced at a predetermined pitch, and a plurality of parallel elongatestriped control electrodes 4 extending over thelayer 2 while crossing with an overpass at regular angles i.e., in the ho-rizontal direction indicated by the arrow H. Thecontrol electrodes 4 havewindows 11 defined therein for drawing electron beams from thelayers 2 therethrough. Thecontrol electrodes 4 are spaced at a predetermined pitch and electrically separated from each other in the vertical direction. Underneath thecontrol electrodes 4, there are disposed insulative layers which are the same as theinsulative layer 3 shown in FIGS. 1(a) and 1(b), but are omitted from illustration in FIG. 7 for the sake of brevity. The electron emission device also includes atransparent substrate 13 of glass or the like which supports a light-emittinglayer 12 of a fluorescent material on its surface facing thecontrol electrodes 4. Thetransparent substrate 13 is spaced from thecontrol electrodes 4. Thelayers 2 and thecontrol electrodes 4 intersect with each other at a matrix of points each serving as a pixel.
Operation of the planar display panel shown in FIG. 7 is as follows: For the display of an image in a standard television system, the electron emission device has asmany cathode layers 2 as the number of pixels in the horizontal direction and asmany control electrodes 4 as the number of scanning lines effective to display the image. A given voltage is applied between a selectedcathode layer 2 and a selectedcontrol electrode 4 to develop an electric field at the edges of thecathode layer 2 for thereby causing thecathode layer 2 to emit a beam of electrons. The electron beam is then applied to the light-emittinglayer 12 which emits light. When the planar display panel is energized in the same manner as an X-Y-matrix plasma display or a liquid crystal display, the planar display panel can display an image produced by the fluorescent light-emittinglayer 12 that glows under electron bombardment.
FIG. 8 shows an electron emission device according to a third embodiment of the present invention, the electron emission device being incorporated in a matrix electron emission source or a planar display panel. The electron emission device shown in FIG. 8 is basically the same as the electron emission device shown in FIG. 7, except that thelayers 2 and thecontrol electrodes 4 shown in FIG. 8 have different configurations. Thelayers 2 and thecontrol electrodes 4 intersect with each other at pixel-forming points or electron emission areas where thelayers 2 and thewindows 11 of thecontrol electrodes 4 are of a zigzag shape for widening regions where electrons are emitted and also uniformizing irregularities of electron emission from the respective pixels.
Thelayers 2 and thecontrol electrodes 4 may extend horizontally and vertically, respectively, i.e., may be angularly shifted by 90° from the position shown in FIGS. 7 and 8.
In each of the above embodiments, the layer of cathode material having a rectangular cross section and the insulative layer are disposed on one surface of the insulative substrate, with the insulative layer being positioned on each side or one side of the layer of cathode material, and the control electrode for drawing electrons from the layer of cathode material is disposed on the insulative layer. Since electrons are emitted from the edges of the cathode layer, it is not necessary to employ a needle-like cathode, and the electron emission device can easily be manufactured.
Inasmuch as the cathode layer and the control electrode can be relatively positioned with high accuracy, the electron emission device can be manufactured with a high yield. The planar display panel or matrix electron emission source which incorporates the electron emission device according to the present invention can emit many electrons uniformly.
An electron emission device according to a fourth embodiment of the present invention will be described below with reference to FIGS. 9 and 10.
Two spacedlayers 2 of a cathode material such as Mo, Ta, W, ZrC, TiC, SiC, LaB₆, or the like are disposed on an electricallyinsulative substrate 1 of glass, ceramic, or the like. On a central surface of theinsulative substrate 1, there is disposed an electricallyinsulative layer 3 of SiO₂, SiO₃N₄, Al₂O₃, or the like which is positioned inwardly of and between confronting edges of, or surrounded by, thelayers 2 in spaced relation thereto. Acontrol electrode 4 for drawing electrodes, which is made of a metal such as Mo, Ta, W, or the like, or any of various other electrically conductive materials, is disposed on theinsulative layer 3. Thecontrol electrode 4 has a bottom surface 4a lying at the same height as or higher than upper surfaces 2c of thecathode layer 2. Each of the cathode layers 2 is of a rectangular cross section and hasopposite edges 2a, 2b. Theedges 2a of the cathode layers 2 confront thecontrol electrode 4. The electron emission device thus constructed serves as a linear, one-dimensional electron emission device.
The electron emission device shown in FIGS. 9 and 10 operates as follows:
Thecontrol electrode 4 and thelayers 2 are connected to a power supply (not shown) such that thecontrol electrode 4 is held at a positive potential and thelayers 2 at a negative potential. when a voltage higher than a predetermined voltage depending on the cathode material of thelayers 2 is applied between thelayers 2 and thecontrol electrode 4, theedges 2a, 2b of thelayer 2 emit electrons. The direction in which the emitted electrons travel is determined by the electric field developed between thecontrol electrode 4 and thelayers 2. Some of the electrons enter thecontrol electrode 4, while the other electrons fly upwardly of thecontrol electrode 4. Inasmuch as thecontrol electrode 4 is disposed between or surrounded by thelayers 2, most of the electrons emitted from thelayers 2 are directed upwardly of thecontrol electrode 4. Because the bottom surface 4a of thecontrol electrode 4 is as high as or higher than the upper surfaces 2c of thelayers 2, the electrons emitted from thelayers 2 travel at a velocity whose upward component is large. Therefore, the number of electrons flying over or upwardly of the control-electrode 4, i.e., the intensity of the electron beams from thelayers 2, is increased. Since theedges 2a of thelayers 2 are disposed in confronting relation to thecontrol electrode 4, respectively, the electric field produced between thecontrol electrode 4 and thelayers 2 is concentrated on theedges 2a, thus increasing the effective field strength at theedges 2a for electron emission, with the advantage that the voltage applied to emit electrons may be reduced.
A process of manufacturing the electron emission device shown in FIGS. 9 and 10 will be described below with reference to FIGS. 11(a) through 11(e).
First, as shown in FIG. 11(a), a thin film of a cathode material such as Mo, Ta, W, ZrC, TiC, SiC, LaB₆, or the like, which will formcathode layers 2, is deposited to a thickness ranging from 300 nm to 500 nm on an electricallyinsulative substrate 1 of glass, ceramic, or the like by a thin film fabrication process such as electron beam evaporation, sputtering, ion beam evaporation, screen printing, or the like. Then, resists 14 are deposited on opposite sides of the thin film by photolithography, the resists 14 being spaced from each other by a distance W1 ranging from 5 µm to 60 µm and having a length ranging from 10 µm to 1 mm. Thereafter, as shown in FIG. 11(b), a central area of the thin film, which is not covered with the resists 14, is etched away by an etching solution, which may be a mixed solution of H₃PO₄, CH₃COOH, HNO₃, and H₂O for Mo, or a mixed acid of HNO₃ and HF for Ta. Then, the resists 14 are removed, leavinglayers 2 of cathode material on the opposite sides of theinsulative substrate 1. As shown in FIG. 11(c), resists 15 are deposited in covering relation to thelayers 2, respectively, by photolithography, the resists 15 being spaced from each other by a distance ranging from 3 µm to 50 µm and having a length ranging from 10 µm to 1 mm. Then, as shown in FIG. 11(d), a thin film of SiO₂, Al₂O₃, Si₃N₄, or the like, which will form aninsulative layer 3, and then a thin film of Mo, Cr, Ta, W, or the like, which will form acontrol electrode 4, are deposited to a thickness ranging from 500 nm to 1 µm and a thickness ranging from 200 nm to 300 nm, respectively, on the surface formed thus far by ECR plasma CVD, electron beam evaporation, sputtering, ion beam evaporation, of the like. Thereafter, the resists 15 are lifted off together with the thin films thereon, leaving the central thin films which serve respectively as theinsulative layer 3 and thecontrol electrode 4. The linear, one-dimensional electron emission device shown in FIGS. 9 and 10 is now completed.
A voltage was applied to the electron emission device thus fabricated with thecontrol electrode 4 at a positive potential and thelayers 2 at a negative potential. When a voltage ranging from 50 V to 80 V was applied, the electron emission device started emitting electrons. When a voltage of 100 V was applied, an emission current ranging from 50 µA to 100 µA was produced. When the electron beam emitted from the electron emission device was focused on a fluorescent surface by a focusing electrode, the fluorescent surface displayed a good linear electron beam pattern or image having a width ranging from 5 µm to 50 µm and a length ranging from 10 µm to 1 mm.
FIG. 12 illustrates an electron emission device according to a fifth embodiment of the present invention. The electron emission device shown in FIG. 12 is similar to the electron emission device shown in FIGS. 9 and 10. Therefore, those parts shown in FIG. 12 which are identical to those shown in FIGS. 9 and 10 are denoted by identical reference numerals, and will not be described in detail.
The electron emission device shown in FIG. 12 additionally has an electricallyconductive layer 16 disposed in theinsulative layer 3 and electrically connected to thecontrol electrode 4 and an electricallyconductive layer 17 disposed in theinsulative layer 3 and electrically conndcted to theconductive layer 16. Theconductive layer 17 is disposed centrally on theinsulative substrate 1 and is of a long configuration extending in a direction normal to the sheet of FIG. 12. Theconductive layer 17 serves as a lead electrically connected to thecontrol electrode 4, for applying a voltage between thecontrol electrode 4 and the cathode layers 2.
When a voltage, which is higher than a certain voltage depending on the cathode material of thelayers 2,is applied between thecontrol electrode 4 through theconductive layers 16, 17 and the cathode layers 2, with thecontrol electrode 4 at a positive potential and the cathode layers 2 at a negative potential, electrons are emitted from theedges 2a of thecathode layer 2 and combined into a concentrated electron beam at the center of the electron emission device by thecontrol electrode 4. Since the electric field produced between thecontrol electrode 4 and thecathode layer 2 is concentrated on theedges 2a, the effective field strength is increased to facilitate electron emission from theedges 2a. As a consequence, the voltage applied to the electron emission device for electron emission is lowered.
FIGS. 13(a) through 13(e) show a process of manufacturing the electron emission device shown in FIG. 12.
First, as shown in FIG. 13(a), a thin film of a cathode material such as Mo, W, ZrC, LaB₆, or the like, which will formcathode layers 2 and an electricallyconductive layer 17, is deposited to a thickness ranging from 300 nm to 500 nm on an electricallyinsulative substrate 1 of glass, ceramic, or the like by a thin film fabrication process. Then, resists 18, 19 are deposited on opposite sides and a central area of the thin film by photolithography, the resist 19 having a width L1 ranging from 3 µm to 50 µm and being spaced from the resists 18 by a distance L2 ranging from 5 µm to 10 µm. The resists 18, 19 have a length ranging from 10 µm to 1 mm. Thereafter, as shown in FIG. 13(b), those areas of the thin film which are not covered with the resists 18, 19, are etched away by an etching solution. Then, the resists 18, 19 are removed, leavinglayers 2 of cathode material on the opposite sides of theinsulative substrate 1 and an electricallyconductive layer 17 on the central area thereof. As shown in FIG. 13(c), a thin film such as Al, Ta, or the like, which will form aninsulative layer 3 and an electricallyconductive layer 16, and then a thin film of Mo, Cr, W, or the like, which will form acontrol electrode 4, are deposited to a thickness ranging from 500 nm to 1 µm and a thickness ranging from 200 nm to 300 nm, respectively, on the surface formed thus far by evaporation or the like. In addition, a resist-20 having a width ranging from 5 µm to 60 µm and a length ranging from 10 µm to 1 mm is deposited centrally on the uppermost thin film by evaporation or the like. As shown in FIG. 13(d), the two thin films which are not covered with the resist 20 are etched away, thereby leaving the thin films beneath the resist 20. The upper thin film serves as acontrol electrode 4. Then, as shown in FIG. 13(e), outer surfaces of the thin film below thecontrol electrode 4 are anodized with thecontrol electrode 4 connected as an anode, thereby forming aninsulative layer 3. If the thin film beneath thecontrol electrode 4 is made of Al, then theinsulative layer 3 is made of Al₂O₃ with an electricallyconductive layer 16 of Al being disposed therein. If the thin film beneath thecontrol electrode 4 is made of Ta, theinsulative layer 3 is made of Ta₂O₅ with an electricallyconductive layer 16 of Ta being disposed therein. Thereafter, the resist 20 is removed, completing the linear, one-dimensional electron emission device shown in FIG. 12.
The electron emission device thus fabricated was tested for electron emission characteristics in the same manner as with the fourth embodiment. When a voltage of 100 V was applied, an emission current ranging from 50 µA to 100 µA was produced. When the electron beam emitted from the electron emission device was focused on a fluorescent surface by a focusing electrode, the fluorescent surface displayed a good linear electron beam pattern or image having a width ranging from 5 µm to 50 µm.
FIG. 14 illustrates an electron emission device according to a sixth embodiment of the present invention. In the fifth embodiment, theconductive layer 17 is disposed on theinsulative substrate 1. According to the sixth embodiment, theconductive layer 17 is embedded in theinsulative substrate 1, and theconductive layer 16, theinsulative layer 3, and thecontrol electrode 4 are disposed on theconductive layer 17 and theinsulative substrate 1. The cathode layers 2 are disposed on theinsulative substrate 1 one on each side of or in surrounding relation to theconductive layer 16, theinsulative layer 3, and thecontrol electrode 4. The electron emission device according to the sixth embodiment also offers the same advantages as the electron emission devices according to the fourth and fifth embodiments.
FIG. 15 shows an electron emission device according to a seventh embodiment of the present invention. In the seventh embodiment, an electricallyinsulative layer 21 is disposed on theinsulative substrate 1, and theconductive layer 17 is embedded in theinsulative layer 21. Theconductive layer 16, theinsulative layer 3, and thecontrol electrode 4 are disposed on theconductive layer 17 and theinsulative substrate 21. The cathode layers 2 are disposed on theinsulative substrate 21 one on each side of or in surrounding relation to theconductive layer 16, theinsulative layer 3, and thecontrol electrode 4. The electron emission device according to the seventh embodiment also offers the same advantages as the electron emission devices according to the fourth and fifth embodiments.
FIGS. 16(a) through 16(c) show, in plan, electron emission devices according to eighth through tenth embodiments, respectively, of the present invention.
In each of the fourth through seventh embodiments, the electron emission device is in the form of a linear, one-dimensional electron emission device. According to the eighth through tenth embodiments, as shown in FIGS. 16(a) through 16(c), acontrol electrode 4 is disposed in a central position, and alayer 2 of cathode material is disposed in surrounding relation to thecontrol electrode 4. More specifically, in FIG. 16(a), acircular control electrode 4 is surrounded by a ring-shapedcathode layer 2. In FIG. 16(b), al. atriangular control electrode 4 is surrounded by three rectangular cathode layers 2. In FIG. 16(c), a five-pointed star-shapedcontrol electrode 4 is surrounded by five triangular cathode layers 2. The electron emission devices shown in FIGS. 16(a) through 16(c) are as advantageous as the electron emission devices according to the fourth and fifth embodiments.
Thecontrol electrode 4 and the cathode layer orlayers 2 are however not limited to the illustrated shapes in the above embodiments.
In the fourth through tenth embodiments, since the control electrode is disposed inwardly of the cathode layer or layers, the electron beam which is emitted from the cathode layer or layers when a voltage is applied between the cathode layer or layers and the control electrode is caused to travel upwardly of the control electrode, i.e., toward the center of the electron emission device. Therefore, the emitted electron beam is converged, and hence is of highly defined, high-quality nature. Since the electron emission device is simple in structure, it can easily be manufactured with a high yield, and is highly reliable in operation. As the edges of the cathode layer or layers confront the control electrode, the produced electric field is concentrated on the edges, so that the voltage required by the electron emission device for electron emission may be low.
FIGS. 17(a) through 17(c) illustrate an electron emission device according to an eleventh embodiment of the present invention.
Acircular layer 2 of a cathode material such as Mo, Ta, W, ZrC, LaB₆, or the like is disposed centrally on an electricallyinsulative substrate 1 of glass, ceramic, or the like. On thecathode layer 2, there is disposed an electricallyinsulative layer 22 of SiO₂, SiO₃N₄, Al₂O₃, or the like which is small enough to allow anouter edge 2a of thecathode layer 2 to be exposed. A first control electrode 4-1 of Mo, Ta, Cr, Al, Au, or the like is disposed on theinsulative layer 22. An electricallyinsulative layer 3 of SiO₂, SiO₃N₄, Al₂O₃, or the like is disposed on an outer peripheral marginal edge of theinsulative substrate 1 around thecathode layer 2, theinsulative layer 22, and the first control electrode 4-1 in radially spaced relation thereto. A second control electrode 4-2 of Mo, Ta, Cr, Al, Au, or the like is disposed on theinsulative layer 3. The first and second control electrodes 4-1, 4-2 are electrically connected to each other. More specifically, as shown in FIGS. 17(a) and 17(c), an electricallyinsulative layer 23 of SiO₂, SiO₃N₄, Al₂O₃, or the like is disposed on an exposed area of thecathode layer 2 and an exposed area of theinsulative substrate 1 which lies between thecathode layer 2 and thesurrounding insulative layer 3. The first and second control electrodes 4-1, 4-2 are electrically connected by anelectric connector 24 of Mo, Ta, Cr, Al, Au, or the like which is disposed on theinsulative layer 23.
Operation of the electron emission device shown in FIGS. 17(a) through 17(c) will be described below.
Thelayer 2 and the first and second control electrodes 4-1, 4-2 are connected to a power supply (not shown) such that thelayer 2 is held at a negative potential and the first and second control electrodes 4-1, 4-2 at a positive potential. When a voltage higher than a predetermined voltage depending on the cathode material of thelayer 2 is applied between thelayer 2 and the control electrodes 4-1, 4-2, a developed electric field is concentrated on theedge 2a of thelayer 2 to cause theedge 2a to emit electrons into a surrounding evacuated space. The emitted electrons travel along electric lines of force that are determined under the applied voltage between the first and second control electrodes 4-1, 4-2 and thelayer 2. If the first control electrode 4-1 did not exist, the electric lines of force would be directed toward the second control electrode 4-2, i.e., radially outwardly from the center of the electron emission device, so that the electron beam would spread apart. Since the first control electrode 4-1 is disposed at the center of the electron emission device, the generated electron beam is directed toward the center of the electron emission device, rather than radially outwardly, and hence is concentrated into a highly defined, high-quality electron beam.
Theinsulative layer 3 and the second control electrode 4-2 may be disposed on each side of thecathode layer 2, theinsulative layer 22, and the first control electrode 4-1, rather than surround them as shown.
FIGS. 18(a) and 18(b) show an electron emission device according to a twelfth embodiment of the present invention.
An electricallyinsulative substrate 1 supports thereon an electricallyinsulative layer 25, and a ring-shapedlayer 2 of cathode material is disposed centrally on theinsulative layer 25. Another electricallyinsulative layer 22 is disposed on the ring-shapedlayer 2 of the cathode material and an exposed area which lies on the inward side of the ring-shapedcathode layer 2. Theinsulative layer 22 is small enough to expose anouter edge 2a of thecathode layer 2. A first control electrode 4-1 is disposed on theinsulative layer 22. An electricallyinsulative layer 3 is disposed on an outer peripheral marginal edge of theinsulative substrate 25 around thecathode layer 2, theinsulative layer 22, and the first control electrode 4-1 in radially spaced relation thereto. A second control electrode 4-2 of is disposed on theinsulative layer 3. The first and second control electrodes 4-1, 4-2 are electrically connected to each other by an insulatedelectric connector 26 which extends through the inside of theinsulative layer 22, the inside of theinsulative layer 25, and the inside of theinsulative layer 3.
The components of the electron emission device shown in FIGS. 18(a) and 18(b) are of the same materials as those of the electron emission device according to the eleventh embodiment. Also, the electron emission device shown in FIGS. 18(a) and 18(b) operates in the same manner as the electron emission device according to the eleventh embodiment.
An electron emission device according to a thirteenth embodiment of the present invention is shown in FIG. 19. Those parts of the electron emission device shown in FIG. 19 which are identical to the electron emission device according to the eleventh embodiment shown in FIGS. 17(a) through 17(c) are denoted by identical reference numerals, and will not be described in detail. As shown in FIG. 19, the electron emission device additionally includes anelectrically insulative layer 27 of SiO₂, SiO₃N₄, Al₂O₃, or the like disposed on the second control electrode 4-2, and a third control electrode 4-3 of Mo, Ta, W, Cr, Al, Au, or the like disposed on theinsulative layer 27.
The electron emission device shown in FIG. 19 operates as follows:
Thelayer 2 and the first and second control electrodes 4-1, 4-2 are connected to a power supply (not shown) such that thelayer 2 is held at a negative potential and the first and second control electrodes 4-1, 4-2 at a positive potential. When a voltage higher than a predetermined voltage depending on'the cathode material of thelayer 2 is applied between thelayer 2 and the control electrodes 4-1, 4-2, a developed electric field is concentrated on theedge 2a of thelayer 2 to cause theedge 2a to emit electrons into a surrounding evacuated space. The emitted electrons is caused by the first control electrode 4-1 to travel toward the center of the electron emission device, resulting in a convergent electron beam, as described before with reference to the eleventh embodiment. If the voltage applied between thecathode layer 2 and the first and second control electrodes 4-1, 4-2 were lower than the predetermined voltage, no electrons would be emitted from thecathode layer 2 into the surrounding evacuated space. Therefore, the number of electrons emitted from thecathode layer 2 can be controlled when the voltage applied between thecathode layer 2 and the first and second control electrodes 4-1, 4-2 is controlled. When the third control electrode 4-3 is kept at a potential higher than the potential of the first and second control electrodes 4-1, 4-2, the electrons emitted in the evacuated space are accelerated upwardly of the electron emission device. Consequently, the electron beam can easily be drawn from the electron emission device while being prevented from spreading outwardly therefrom.
FIGS. 20(a) through 20(g) show a process of manufacturing the electron emission device illustrated in FIG. 19.
As shown in FIG. 20(a), alayer 2 of a cathode material such as Mo, W, or the like is deposited by sputtering on a central area of an electricallyinsulative substrate 1 of glass which has a thickness of 1 mm. Thelayer 2 has a thickness ranging from 200 nm to 400 nm, a width ranging from 10 µm to 50 µm, and a length of 200 µm. Then, as shown in FIG. 20(b), resists 28 having a thickness of 1.5 µm and spaced from each other by a distance ranging from 5 µm to 48 µm are deposited on an exposed area of theinsulative substrate 1 and opposite sides of thecathode layer 2. As shown in FIG. 20(c), a film of SiO₂ or the like, which will form an electricallyinsulative layer 22, and a electrically conductive film of Mo, Cr, or the like, which will form a first control electrode 4-1, are successively deposited to a thickness ranging from 800 nm to 1 µm and a thickness ranging from 200 nm to 400 nm, respectively, on the resist 28 and thecathode layer 2 by electron beam evaporation or sputtering. Then, the resist 28 is lifted off, thereby forming anelectrically insulative layer 22 and a first control electrode 4-1 on thecathode layer 2, as shown in FIG. 20(d). As shown in FIG. 20(e), amask 29 is disposed in covering relation to the first control electrode 4-1, theinsulative layer 22, thecathode layer 2, and an exposed area of theinsulative substrate 1, themask 29 having a width ranging from 12 µm to 55 µm and a thickness of 2.5 µm. Then, as shown in FIG. 20(f), a film of SiO₂, which will form an electricallyinsulative layer 3, an electrically conductive film of Mo or Cr, which will form a second control electrode 4-2, a film of SiO₂ or the like, which will form an electricallyinsulative layer 27, and an electrically conductive film of Mo or Cr, which will form a third conductive electrode 4-3, are successively deposited to a thickness ranging from 800 nm to 1 µm, a thickness ranging from 200 nm to 400 nm, a thickness ranging from 800 nm to 1 µm, and a thickness ranging from 200 nm to 400 nm, respectively, on the surface thus far by electron beam evaporation or sputtering. Thereafter, themask 29 is lifted off, providing an electron emission device including a second control electrode 4-2 and a third control electrode 4-3, as shown in FIG. 20(g). When an electron beam emitted from the electron emission device thus fabricated was focused on a fluorescent surface by a focusing electrode, the fluorescent surface displayed a good linear electron beam pattern or image having a width ranging from 10 µm to 55 µm and a length of 200 µm.
In the eleventh through thirteenth embodiments, the electron beam which is emitted from the cathode layer when a voltage is applied between the cathode layer and the first and second control electrodes is prevented by the first control electrode from traveling toward the second control electrode, i.e., toward the center of the electron emission device. Therefore, the emitted electron beam is converged, and hence is of highly defined, high-quality nature. Since the electron emission device is simple in structure, it can easily be manufactured with a high yield, and is highly reliable in operation.
The third control electrode is effective to accelerate the emitted electron beam, which can thus be drawn easily and stably from the electron emission device.
FIGS. 21(a) through 21(c) illustrate an electron emission device according to a fourteenth embodiment of the present invention.
Abase electrode 30 of electrically conductive material is disposed on an electricallyinsulative substrate 1 of glass or the like, and alayer 2 of cathode material, to which an electric current is supplied from thebase electrode 30, is disposed on thebase electrode 30. The cathode material of thelayer 2 may be a material having a high work function and a high melting point, such as SiC, ZrC, TiC, Mo, W, or the like, for example. Thecathode layer 2 is of a four-pointed star-shaped or crisscross configuration, as viewed in plan, and has a rectangular or trapezoidal cross section which has anouter edge 2a. Thecathode layer 2 has four outwardly extending arms each having a wedge shape as viewed in plan, the arm having a width W that varies progressively linearly from zero to a certain dimension in an inward direction from the distal end toward the center of thecathode layer 2. However, thecathode layer 2 is not limited to the illustrated configuration, the the width W may not necessarily vary linearly providing it should vary progressively. The electron emission device also includes anelectrically insulative layer 31 which is disposed on thebase electrode 30 in an area beneath an outer marginal edge of thecathode layer 2 and in an outer area free of or not covered by thecathode layer 2. An electricallyinsulative layer 3 is disposed on theinsulative layer 31 and outwardly spaced from thecathode layer 2 in complementarily surrounding relation thereto, and acontrol electrode 4 is disposed on theinsulative layer 3. Theinsulative layer 3 is made of a material such as Al₂O₃, SiO₂, or the like, and has a thickness equal to or greater than the thickness of thecathode layer 2. Thecontrol electrode 4, which serves to draw electrons from thecathode layer 2, is made of metal or the like.
The electron emission device shown in FIGS. 21(a) through 21(c) operates as follows:
A voltage is applied between thecathode layer 2 and thecontrol electrode 4 such that thecathode layer 2 is kept at a negative potential and thecontrol electrode 4 at a positive potential. Electric lines of force are concentrated on anouter edge 2a of thecathode layer 2, developing an intensive electric field at theedge 2a. Since the wedge-shaped arms of thecathode layer 2 and the complementarily wedge-shaped recesses of thecontrol electrode 4 have varying widths, the field strength of the electric field at theouter edge 2a varies depending on the position on thecathode layer 2. Therefore, even if thecathode layer 2 and thecontrol electrode 4 have pattern accuracy differences when they are formed, thecathode layer 2 always has edge areas where there is developed a field strength required to emit electrons therefrom. Consequently, the electron emission device has stable electron emission characteristics. Thecathode electrode 4 is positioned at the same height as or higher than the upper surface of thecathode layer 2, so that electrons emitted from theedge 2a of thecathode layer 2 are prevented from spreading, but are controlled to travel in a direction substantially perpendicular to the upper surface of thecathode layer 2. Accordingly, the emitted electron beam is well defined and of high quality. The wedge-shaped arms of thecathode layer 2 have pointed outer ends on which the electric field can be concentrated for directing the electron beam perpendicularly to the upper surface of thecathode layer 2.
A process of manufacturing the electron emission device shown in FIGS. 21(a) through 21(c) will be described below with reference to FIGS. 22(a) through 22(f).
As shown in FIG. 22(a), abase electrode 30 of an electrically conductive material such as Al, Ta, or the like is deposited to a predetermined thickness on an electricallyinsulative substrate 1 of glass or the like by vacuum evaporation, sputtering, or the like. Then, an electrically conductive film of SiC, ZrC, TiC, Mo, W, or the like, which will form acathode layer 2, is deposited to a predetermined thickness on thebase electrode 30. In addition, afilm 32 of liftoff material is deposited on the uppermost conductive film, theliftoff material film 32 being thicker than an electrically insulative layer 3 (described later). The liftoff material may be a metal or an insulative material which can withstand an etching solution used to etch thecathode layer 2 or such that a solution used to remove theliftoff material film 32 does not erode other materials when the liftoff material will be removed.
Then, as shown in FIG. 22(b), aphotoresist 33 is deposited on theliftoff material film 32 in a pattern of thecathode layer 2. Using thephotoresist 33 as a protective film, theliftoff material film 32 and the conductive film therebeneath are etched away, thus leaving theliftoff material film 32 and the conductive film below thephotoresist 33. As shown in FIG. 22(c), only the conductive film beneath theliftoff material film 32 is etched at its outer peripheral edge into a pattern smaller than the lift-off material film 32.
Then, as shown in FIG. 22(d), at least the surface of thebase electrode 30 of conductive material which is not covered with thecathode layer 2 is anodized into an electricallyinsulative layer 31. If the conductive material of thebase electrode 30 is Al, then theoxidized insulative layer 31 of Al₂O₃ is formed. If the conductive material of thebase electrode 30 is Ta, then theoxidized insulative layer 31 of Ta₂O₅ is formed. It is preferable that theinsulative layer 31 extend to a certain extent beneath the outer peripheral edge of thecathode layer 2.
As shown in FIG. 22(e), thephotoresist 33 is removed, and an electrically insulative material, which will form an electricallyinsulative layer 3, and a metal material, which will form acontrol electrode 4, are successively deposited on the surface formed thus far by sputtering or the like. The insulative material, which will form aninsulative layer 3, is of a thickness equal to or greater than the thickness of thecathode layer 2. Since thephotoresist 33 has been removed before the deposition of the insulative material and the metal material, the deposited materials are not smeared by thephotoresist 33 which would otherwise be decomposed when the overall assembly is heated to increase the bonding strength between theinsulative layer 31, theinsulative layer 3, and thecontrol electrode 4. If theinsulative layer 3 is to be sputtered, then the surface of theinsulative layer 31 should preferably be purified in advance by inert gas ions because foreign matter may have been attached to theinsulative layer 31 or it may have been contaminated in the previous steps.
Then, theliftoff material film 32 is removed to remove the insulative layer and the metal layer thereon at the same time, thus exposing thecathode layer 2 including itsedge 2a. Theinsulative layer 3 and thecontrol electrode 4 are now formed in surrounding and spaced relation to thecathode layer 2. The metal material of thecontrol electrode 4 should be a chemically and physically stable material so that it is not eroded when theliftoff material film 32 is removed.
FIGS. 23(a) through 23(g) show another process of manufacturing the electron emission device according to the fourteenth embodiment.
As shown in FIG. 23(a), abase electrode 30 of an electrically conductive material such as Al, Ta, Mo, or the like is deposited to a predetermined thickness on an electricallyinsulative substrate 1 of glass or the like by vacuum evaporation, sputtering, or the like. Then, an electricallyinsulative film 34 of SiO₂, for example, in a pattern of a cathode layer 2 (described later) is deposited on thebase electrode 30. More specifically, aninsulative film 34 is deposited to a certain thickness on thebase electrode 30, a photoresist pattern (not shown) is deposited on theinsulative film 34, and theinsulative layer 34 is etched, using the photoresist patter as a mask (alternatively, theinsulative layer 34 may be a photoresist pattern itself).
Then, as shown in FIG. 23(b), at least the exposed surface of thebase electrode 30, which is not covered with theinsulative layer 34, is processed into an electricallyinsulative layer 31. More specifically, if the conductive material of thebase electrode 30 is Al or Ta, then the exposed surface of thebase electrode 30 may be anodized or thermally oxidized in an oxygen atmosphere. If the conductive material of thebase electrode 30 is Al, then theoxidized insulative layer 31 of Al₂O₃ is formed. If the conductive material of thebase electrode 30 is Ta, then theoxidized insulative layer 31 of Ta₂O₅ is formed. It is preferable that theinsulative layer 31 extend to a certain extent beneath the outer peripheral edge of theinsulative layer 34.
Then, as shown in FIG. 23(c), theinsulative layer 34 is removed, and an electrically conductive film of SiC, ZrC, TiC, Mo, W, or the like, which will form acathode layer 2, is deposited to a predetermined thickness on thebase electrode 30 by vacuum evaporation. In addition, afilm 35 of liftoff material is deposited as a covering material on the uppermost conductive film, theliftoff material film 35 being thicker than an electrically insulative layer 3 (described later). The liftoff material may be a metal or an insulative material which can withstand an etching solution used to etch thecathode layer 2 or such that a solution used to remove theliftoff material film 35 does not erode other materials when the liftoff material will be removed.
Then, as shown in FIG. 23(d), aphotoresist 36 is deposited on theliftoff material film 35 in a pattern of thecathode layer 2, i.e., in the same position as theinsulative layer 34. Using thephotoresist 33 as a protective film, theliftoff material film 35 and the conductive film therebeneath are etched away, thus leaving theliftoff material film 35 and the conductive film below the photoresist 36 (theliftoff material film 35 may be a photoresist itself). As shown in FIG. 23(e), only the conductive film beneath theliftoff material film 35 is etched at its outer peripheral edge into a pattern smaller than theliftoff material film 35.
As shown in FIG. 23(f), thephotoresist 36 is removed, and an electrically insulative material, which will form an electricallyinsulative layer 3, and a metal material, which will form acontrol electrode 4, are successively deposited on the surface formed thus far by sputtering or the like. The insulative material, which will form aninsulative layer 3, is of a thickness equal to or greater than the thickness of thecathode layer 2.
Then, theliftoff material film 35 is removed to remove the insulative layer and the metal layer thereon at the same time, thus exposing thecathode layer 2 including itsedge 2a. Theinsulative layer 3 and thecontrol electrode 4 are now formed in surrounding and spaced relation to thecathode layer 2. The metal material of thecontrol electrode 4 should be a chemically and physically stable material so that it is not eroded when theliftoff material film 35 is removed.
FIGS. 24(a) and 24(b) show an electron emission device according to a fifteenth embodiment of the present invention, the electron emission device being incorporated in a planar display panel.
As shown in FIGS. 24(a) and 24(b), a plurality of parallel, vertically elongatestriped base electrodes 30 are disposed on an electricallyinsulative base 1, thebase electrodes 30 being horizontally spaced at a predetermined pitch, and a plurality of four-pointed star-shapedcathode layers 2 are disposed on thebase electrodes 30. Electrically insulative layers 31 are disposed on at least the surfaces of thebase electrodes 30 which are not covered with the cathode layers 2. Electrically insulative layers 3 andcontrol electrodes 4 are successively disposed on the insulative layers 31 and theinsulative base 1 and positioned outwardly of or in surrounding relation to the cathode layers 2 in spaced relation thereto. Thecontrol electrodes 4 are in a horizontally elongate striped pattern crossing thebase electrodes 30 with an over pass at regular angles, and have complementary windows opening over the cathode layers 2. Thecontrol electrodes 4 are vertically spaced at a prescribed pitch and are electrically isolated from each other. Atransparent substrate 13 is positioned in front of thecontrol electrodes 4 and spaced therefrom. Thetransparent substrate 13 supports, on its inner surface facing thecontrol electrodes 4, a transparent electricallyconductive film 37 and a fluorescent light-emittinglayer 12 which are successively disposed thereon. A thin film of Al may be disposed, in place of the transparentconductive film 37, on the light-emittinglayer 12, as with an ordinary cathode-ray tube.
The planar display panel thus constructed operates as follows:
For the display of an image in a standard television system, the electron emission device has asmany base electrodes 30 supportingcathode layers 2 as the number of pixels in the horizontal direction and asmany control electrodes 4 as the number of scanning lines effective to display the image. A given voltage is applied between a selectedbase electrode 30 and a selectedcontrol electrode 4 to develop an intensive electric field for thereby causing thecathode layer 2 to emit electrons. The electrons are then applied to the light-emittinglayer 12 which emits light. By varying the voltage applied between thebase electrode 30 and thecontrol electrode 4 or the time in which the voltage is applied, the intensity of light emitted from the light-emittinglayer 12 is varied. Therefore, when the planar display panel is energized in the same manner as an X-Y-matrix plasma display or a liquid crystal display, the planar display panel can display an image produced by the fluorescent light-emittinglayer 12 that glows under electron bombardment.
As described above, thebase electrodes 30 and thecontrol electrodes 4 are disposed perpendicularly to each other, and the cathode layers 2 located where thebase electrodes 30 and thecontrol electrodes 4 intersect with each other have progressively varying widths to provide many electron emission regions. Therefore, the planar display panel or matrix electron emission source can emits an increased number of electrons per pixel and has uniform electron emission characteristics.
While there are fourcathode layers 2 in each point of intersection of thebase electrodes 30 and thecontrol electrodes 4 in the illustrated embodiment, more orless cathode layers 2 may be provided in each point of intersection.
With the electron emission device according to the fourteenth embodiment, since the wedge-shaped arms of thecathode layer 2 have varying widths, even if thecathode layer 2 and thecontrol electrode 4 have pattern accuracy differences when they are formed, thecathode layer 2 always has edge areas where there is developed a field strength required to emit electrons therefrom, and the developed electric field is easily concentrated on those edge areas. Consequently, the electron emission device has stable electron emission characteristics. The wedge-shaped arms of thecathode layer 2 have pointed outer ends on which the electric field can be concentrated to a maximum degree.
Theinsulative layer 31 is disposed on the surface of thebase electrode 30 and thecontrol electrode 4 is disposed on theinsulative layer 3 which is in turn disposed on theinsulative layer 31. Thus, the dielectric strength between thecathode layer 2 and thecontrol electrode 4 is increased to facilitate concentration of the electric field on the edges of thecathode layer 2. Consequently, the electron emission efficiency of the electron emission device is high, and so is the reliability of the electron emission device. Thecathode electrode 4 is positioned at the same height as or higher than the upper surface of thecathode layer 2, so that electrons emitted from theedge 2a of thecathode layer 2 are prevented from spreading. The emitted electron beam is therefore of high quality.
The matrix electron emission source incorporating the electron emission device according to the fifteenth embodiment is capable of uniformly emitting many electrons.
According to the process of manufacturing the electron emission device of the fourteenth embodiment, the base electrode is deposited by sputtering or the like, the surface of the base electrode is anodized or thermally oxidized, the cathode layer is deposited by sputtering, etching, or the like, and the insulative layer and the control electrode on the insulative layer on the surface of the base electrode are deposited by sputtering or the like. Since electrons are emitted from the edge of the cathode layer, the cathode is not required to be formed as a needle point, and hence can be manufactured with ease. The control electrode is shaped complementarily to the cathode layer which has been formed to a certain shape. Therefore, the cathode layer and the control layer are positionally related to each other with high accuracy. The electron emission device thus fabricated has a high electron emission efficiency, and provides a high dielectric voltage between the cathode layer and the control electrode. The electron emission device therefore can emit electrodes highly reliably. The electron emission device can also be manufactured easily with a high yield. Furthermore, the electron emission device can emit a high-quality convergent electron beam which is prevented from spreading apart.
Although certain preferred embodiments have been shown and described, it should be understood that many changes and modifications may be made therein without departing from the scope of the appended claims.
An electron emission device is employed as an electron emission source in various applications using an electron beam. The electron emission device has a cathode layer having an edge, and a control electrode spaced and electrically insulated from the cathode layer, for drawing electrons from said edge of the cathode layer. When a voltage is applied between the cathode layer and the control electrode, a developed electric field is concentrated on the edge of the cathode layer to cause the edge to emit electrons. The electron emission device can easily be manufactured with a high yield since it does not have a needle tip for emitting electrons. A method of manufacturing the electron emission device is also disclosed.

Claims

An electron emission device comprising:
an insulative substrate (1), a cathode layer (2) disposed on the insulative substrate (1), insulative means disposed on the insulative substrate (1) to be spaced from the cathode layer (2), and electron drawing means disposed on the insulative means for drawing electrons from the cathode layer (2) in a direction upwardly away from the insulative substrate (1),characterized in that
the cathode layer (2) is shaped in a rectangular cross section to have a pair of opposite edges (2a and 2b) on its upper surface (2c),
the insulative means comprises a pair of insulative layers (3) between which the cathode layer (2) is disposed at regular spaces,
the electron drawing means comprises a pair of control electrodes (4) disposed on the insulative layers (3) for controlling the electrons depending on a difference in electric potential between the cathode layer (2) and the control electrodes (4),
the thickness of the insulative layers (3) is equal to or larger than that of the cathode layer (2) so that the bottom surfaces (4a) of the control electrodes (4) are at a level equal to or higher than the upper surface (2c) of the cathode layer (2), and
the opposite edges (2a and 2b) of the cathode layer (2) are disposed in a confronting relation to the control electrodes (4).
An electron emission device according to claim 1,characterized in that
the cathode layer (2) comprises a plurality of parallel cathode layers (2) spaced apart at a first pitch, and
the control electrodes (4) comprises a plurality of parallel control electrodes (4) spaced apart at a second pitch and crossing the parallel cathode layers (2) with an overpass at regular angles, a plurality of electron emission areas (11) surrounded by the parallel control electrodes (4) being formed to emit the electrons from the parallel cathode layers (2).
An electron emission device according to claim 2,characterized in that
the parallel cathode layers (2) and the electron emission areas (11) are respectively formed in a zigzag shape.
An electron emission device according to claim 1,characterized in that
the cathode layer (2) is formed in a criss-cross shape to have four tapered arm portions outwardly extending, and the control electrodes (4) are integrally formed with each other to form a window (11) opened in the criss-cross shape, the control electrodes (4) being equally spaced apart from the cathode layer (2), and the electrons being emitted through the window (11).
An electron emission device according to claim 4,characterized in that
a base electrode (30) electrically connected to a central portion of the cathode layer (2) is further included to supply an electric current to the cathode layer (2), the base electrode (30) extending through the insulative substrate (1).
An electron emission device according to claim 1,characterized in that
the cathode layer (2) comprises a plurality of distributed cathode layers (2) arranged in an orderly matrix which each are formed in a criss-cross shape to have four tapered arm portions outwardly extending, and
the control electrodes (4) are integrally formed with each other to form a plurality of windows opened in the cirss-cross shape, the control electrodes (4) being equally spaced apart from the distributed cathode layers (2), and the electrons being emitted through the windows (11).
An electron emission device comprising:
an insulative substrate (1), a cathode layer (2) disposed on the insulative substrate (1), insulative means disposed on the insulative substrate (1) to be spaced from the cathode layer (2), and electron drawing means disposed on the insulative means for drawing electrons from the cathode layer (2) in a direction upwardly away from the insulative substrate (1),characterized in that
the cathode layer (2) comprises a pair of spaced cathode layers (2) which are shaped in a rectangular cross section to have a pair of opposite edges (2a and 2b) on their upper surface (2c),
the insulative means comprises an insulative layer (3),
the electron drawing means comprises a control electrode (4) for controlling the electrons depending on a difference in electric potential between the cathode layer (2) and the control electrode (4),
the insulative layer (3) and the control electrode (4) are disposed between the spaced cathode layers (2) at regular spaces,
the edges (2a) of the spaced cathode layers (2) confront the control electrode (4), and
the thickness of the insulative layer (3) is equal to or larger than those of the spaced cathode layers (2) so that the bottom surface (4a) of the control electrode (4) at a level equal to or higher than the upper surfaces (2c) of the spaced cathode layers (2).
An electron emission device according to claim 7,characterized in that
a conductive layer (16, 17) extending through the insulative layer (3) and electrically connected to the control electrode (4) is further included.
An electron emission device according to claim 7,characterized in that
a first conductive layer (17) embedded in the insulative substrate (1) is further included; and
a second conductive layer (16) extending through the insulative layer (3) and electrically connected to both the first conductive layer (17) and the control electrode (4) is further included.
An electron emission device according to claim 7,characterized in that
a second insulative layer (21) disposed on the insulative substrate (1) is further included;
a first conductive layer (17) embedded in the second insulative substrate (21) is further included; and
a second conductive layer (16) extending through the insulative layer (3) and electrically connected to both the first conductive layer (17) and the control electrode (4) is further included.
An electron emission device according to claim 7,characterized in that
the spaced cathode layers (2) are integrally formed with each other to surround both the insulative layer (3) and the control electrode (4), a unit of the spaced cathode layers (2) being formed in a ring shape and the control electrode (4) being formed in a circular shape.
An electron emission device according to claim 7,characterized in that
the control electrode (4) is formed in a triangular shape, and the cathode layer (2) is composed of three rectangular cathode layers (2) which surround the control electrode (4).
An electron emission device according to claim 7,characterized in that
the control electrode (4) is formed in a five-pointed star shape, and the cathode layer (2) is composed of five triangular cathode layers (2) which surround the control electrode (4).
An electron emission device comprising:
an insulative substrate (1), a cathode layer (2) disposed on the insulative substrate (1), control means for drawing electrons from the cathode layer (2) in a direction upwardly away from the insulative substrate (1), and insulating means for insulating the cathode layer (2) from the control means,characterized in that
the cathode layer (2) is shaped in a rectangular cross section to have an outer edge (2a) on its upper surface,
the insulating means comprises a first insulative layer (22) disposed on the cathode layer (2) to allow the outer edge (2a) of the cathode layer (2) to be exposed, and a second insulative layer (3) disposed on the insulative substrate (1) to surround the cathode layer (2) at regular spaces,
the control means comprises a first control electrode (4-1) disposed on the first insulative layer (22), and a second control electrode (4-2) disposed on the second insulative layer (3) to surround the cathode layer (2) at the regular spaces,
the thickness of the second insulative layers (3) is equal to or lager than that of the cathode layer (2) so that the bottom surface of the second control electrode (4-2) is at a level equal to or higher than the upper surface of the cathode layer (2), and
the outer edge (2a) of the cathode layer (2) is disposed in a confronting relation to the first and second control electrodes (4-1, 4-2).
An electron emission device according to claim 14,characterized in that
the cathode layer (2) is formed in a circular shape, and the level of the first control electrode (4-1) is the same as that of the second control electrode (4-2).
An electron emission device according to claim 14,characterized in that
an electric connector (24) electrically connecting the first and second control electrodes (4-1, 4-2) is further included to equalise electric potentials applied to the first and second control electrodes (4-1, 4-2), the electric connector (24) extending through a part of an electron emission area in which the electrons drawn from the cathode layer (2) are emitted along electric lines of force induced between the cathode layer (2) and the first and second control electrodes (4-1, 4-2).
An electron emission device according to claim 14,characterized in that
an insulated electric connector (26) electrically connecting the first and second control electrodes (4-1, 4-2) is further included to equalise electric potentials applied to the first and second control electrodes (4-1, 4-2), the insulated electric connector (26) extending through the first insulative layer (22), a hollow portion opened in the cathode layer (2), a third insulative layer (25) additionally provided on the insulative substrate (1) and the second insulative layer (3).
An electron emission device according to claim 14,characterized in that
the insulating means further includes a third insulative layer (27) disposed on the second control electrode (4-2), and the control means further includes a third control electrode (4-3) disposed on the third insulative layer (27).
A method of manufacturing an electron emission device as claimed in claim 1 by forming a cathode layer (2) on an insulative substrate (1), forming an insulative layer (3) on the insulative substrate (1) to surround the cathode layer (2) at regular spaces, and forming a control electrode (4) on the insulative layer (3) to draw electrons from the cathode layer (2) in a direction upwardly away from the insulative substrate (1),characterized by:
forming the cathode layer (2) which is shaped in a rectangular cross section to have a pair of opposite edges (2a, 2b) on its upper surface;
selectively forming a photoresist (6) on the cathode layer (2);
depositing an insulative material on both the photoresist (6) and the insulative substrate (1), a height of the insulative material being equal to or higher than that of the cathode layer (2);
depositing a metal film on the insulative material, a height of the metal film being lower than that of the photoresist (6) to expose the photoresist (6);
removing the photoresist (6) from the cathode layer (2), together with the insulative material and the metal film deposited on the photoresist (6);
etching the insulative material deposited on the insulative substrate (1) to surround the cathode layer (2) at the regular spaces, the insulative layer (3) being formed of the insulative material etched; and
etching the metal film deposited on the insulative material to have confronting edges of the metal film spaced from each other by a distance larger than a width W of the cathode layer (2), the confronting edges projecting over the insulative layer (3), and the control electrode (4) with the confronting edges being formed of the metal film etched.
A method of manufacturing an electron emission device as claimed in claim 1 by forming a cathode layer (2) on an insulative substrate (1), forming an insulative layer (3) on the insulative substrate (1) to surround the cathode layer (2) at regular spaces, and forming a control electrode (4) on the insulative layer (3) to draw electrons from the cathode layer (2) in a direction upwardly away from the insulative substrate (1), characterized by:
forming the cathode layer (2) which is shaped in a rectangular cross section to have a pair of opposite edges (2a, 2b) on its upper surface;
selectively forming a first metal film (9) on the cathode layer (2), the first metal film (9) having a high melting point;
depositing an insulative material on both the first metal film (9) and the insulative substrate (1), a height of the insulative material being equal to or higher than that of the cathode layer (2);
performing a first heat treatment to increase a bonding strength between the insulative substrate (1) and the insulative material;
depositing a second metal film on the insulative material, a height of the second metal film being lower than that of the first metal film (9) to expose the first metal film (9);
performing a second heat treatment to increase a bonding strength between the second metal film and the insulative material;
removing the first metal film (9) from the cathode layer (2), together with the insulative material and the second metal film deposited on the first metal film (9);
etching the insulative material deposited on the insulative substrate (1) to surround the cathode layer (2) at the regular spaces, the insulative layer (3) being formed of the insulative material etched; and
etching the second metal film deposited on the insulative material to have confronting edges of the second metal film spaced from each other by a distance larger than a width W of the cathode layer (2), the confronting edges projecting over the insulative layer (3), and the control electrode (4) with the confronting edges being formed of the second metal film etched.
A method of manufacturing an electron emission device as claimed in claim 1 by forming a cathode layer (2) on an insulative substrate (1), forming an insulative layer (3) on the insulative substrate (1) to surround the cathode layer (2) at regular spaces, and forming a control electrode (4) on the insulative layer (3) to draw electrons from the cathode layer (2) in a direction upwardly away from the insulative substrate (1), characterized by:
forming the cathode layer (2) which is shaped in a rectangular cross section to have a pair of opposite edges (2a, 2b) on its upper surface;
selectively plating a first metal film (10) on both an upper surface and side walls of the cathode layer (2) to surround the cathode layer (2) with the first metal film (10);
depositing an insulative material on both the first metal film (10) and the insulative substrate (1), a height of the insulative material being equal to or higher than that of the cathode layer (2);
depositing a second metal film on the insulative material, a height of the second metal film being lower than that of the first metal film (10) to expose the first metal film (10); and
removing the first metal film (10) from the cathode layer (2), together with the insulative material and the second metal film deposited on the first metal film (10), the insulative layer (3) being formed of the insulative material not removed, and the control electrode (4) being formed of the second metal film not removed.
A method of manufacturing an electron emission device as claimed in claim 5 by forming a cathode layer (2) on an insulative substrate (1), forming an insulative layer (3) on the insulative substrate (1) to surround the cathode layer (2) at regular spaces, and forming a control electrode (4) on the insulative layer (3) to draw electrons from the cathode layer (2) in a direction upwardly away from the insulative substrate (1), characterized by:
forming a base electrode (30) on the insulative substrate (1), the base electrode being made of a conductive material;
forming a conductive film on the base electrode (30);
forming a lift-off material (32) on the conductive film;
etching the conductive film and the lift-off material (32) in a wedge shape to have a tapered arm portion extending on the base electrode (30);
selectively etching a side wall of the conductive film to reduce a width of the conductive film, the cathode layer (2) being formed of the reduced conductive film and being shaped in a rectangular cross section;
oxidizing a surface portion of the base electrode (30) not covered by the cathode layer (2) to change the surface portion of the base electrode (30) to an oxidized insulative layer (31);
depositing an insulative material on both the lift-off material (32) and the oxidized insulative layer (31), a height of the insulative material being equal to or higher than that of the cathode layer (2);
depositing a metal film on the insulative material, a height of the metal film being lower than that of the lift-off material (32) to expose the lift-off material (32); and
removing the lift-off material (32) from the cathode layer (2), together with the insulative material and the metal film deposited on the lift-off material (32), the insulative layer (3) being formed of the insulative material not removed, and the control electrode (4) being formed of the metal film not removed.
An method of manufacturing an electron emission device according to claim 22, characterized by:
the step of oxidizing a surface portion further includes the step of additionally oxidizing another surface portion of the base electrode (30) positioned beneath an outer peripheral edge of the cathode layer (2).
An method of manufacturing an electron emission device according to claim 22, characterized by:
the step of performing a first heat treatment to increase a binding strength between the insulative material and the oxidized insulative layer (31) is further included after the step of depositing an insulative material; and
the step of performing a second heat treatment to increase a binding strength between the insulative material and the metal film is further included after the step of depositing a metal film.
A method of manufacturing an electron emission device as claimed in claim 5 by forming a cathode layer (2) on an insulative substrate (1), forming an insulative layer (3) on the insulative substrate (1) to surround the cathode layer (2) at regular spaces, and forming a control electrode (4) on the insulative layer (3) to draw electrons from the cathode layer (2) in a direction upwardly away from the insulative substrate (1), characterized by:
forming a base electrode (30) on the insulative substrate (1), the base electrode being made of a conductive material;
forming an insulative layer (34) on said base electrode (30) patterned in a wedge shape to have a tapered arm portion extending on the base electrode (30);
oxidizing a surface portion of the base electrode (30) not covered by the insulative layer (34) to change the surface portion of the base electrode (30) to an oxidized insulative layer (31);
removing the insulative layer (34);
forming a conductive film on both the base electrode (30) and the oxidized insulative layer (31);
forming a lift-off material (35) on the conductive film;
etching the conductive film and the lift-off material (35) in the wedge shape to pattern the conductive film in the same manner as the insulative layer (34);
selectively etching a side wall of the conductive film to reduce a width of the conductive film, the cathode layer (2) being formed of the reduced conductive film and being shaped in a rectangular cross section;
depositing an insulative material on both the lift-off material (35) and the oxidized insulative layer (31), a height of the insulative material being equal to or higher than that of the cathode layer (2);
depositing a metal film on the insulative material, a height of the metal film being lower than that of the lift-off material (35) to expose the lift-off material (35); and
removing the lift-off material (35) from the cathode layer (2), together with the insulative material and the metal film deposited on the lift-off material (35), the insulative layer (3) being formed of the insulative material not removed, and the control electrode (4) being formed of the metal film not removed.
An method of manufacturing an electron emission device according to claim 25, characterized by:
the step of oxidizing a surface portion further includes the step of additionally oxidizing another surface portion of the base electrode (30) positioned beneath an outer peripheral edge of the insulative layer (34).
An method of manufacturing an electron emission device according to claim 25, characterized by:
the step of performing a first heat treatment to increase a binding strength between the insulative material and the oxidized insulative layer (31) is further included after the step of depositing an insulative material; and
the step of performing a second heat treatment to increase a binding strength between the insulative material and the metal film is further included after the step of depositing a metal film.